A 42-year-old woman with Graves disease is hospitalized for elective total thyroidectomy. Her hyperthyroid symptoms have been controlled with methimazole and propranolol, but she still has a goiter. The patient has no other medical problems. She undergoes total thyroidectomy without any immediate operative complications and feels well the next day. Laboratory results are as follows:
| Serum chemistry | |
| Sodium | 141 mEq/L |
| Potassium | 4.4 mEq/L |
| Creatinine | 0.8 mg/dL |
| Calcium | 7.5 mg/dL |
Preoperative electrolyte values were within normal limits. Which of the following medications should be started in this patient?
Show Explanatory Sources
The parathyroid glands are relatively small and indistinct and can be injured during thyroid surgery due to direct trauma, devascularization, or inadvertent removal. Transient or permanent postoperative hypoparathyroidism can occur following thyroidectomy and cause clinically significant hypocalcemia. Patients may be asymptomatic initially but can develop paresthesias (of the lips, mouth, hands, and feet), muscle twitching, or cramps. Worsening hypocalcemia can lead to trismus or tetany with changes in mental status and generalized seizures.
Postoperative supplementation with oral calcium and vitamin D can be used to treat and prevent postoperative hypocalcemia. Calcitriol, the active form of vitamin D, should be chosen over calcidiol as the conversion of calcidiol to calcitriol is dependent on parathyroid hormone, and patients with hypoparathyroidism can have inadequate production of calcitriol.
(Choice A) Alendronate is a bisphosphonate that inhibits osteoclast function. Bisphosphonates can worsen hypocalcemia by decreasing the release of calcium from bone.
(Choice C) Cinacalcet is a calcimimetic that allosterically activates the calcium-sensing receptor in the parathyroid gland, decreasing parathyroid hormone release. Cinacalcet is normally used for secondary hyperparathyroidism in patients on dialysis.
(Choice D) Glucocorticoids (eg, prednisone) can worsen hypocalcemia by decreasing expression of the vitamin D receptor.
(Choice E) The primary treatment modalities for Graves disease include antithyroid drugs (eg, methimazole), thyroidectomy, and radioiodine ablation. This patient has undergone definitive treatment with thyroidectomy and has no indication for radioiodine therapy.
(Choice F) Sevelamer is a nonabsorbable phosphate-binding polymer that decreases absorption of phosphate in the gastrointestinal tract, and is used to treat hyperphosphatemia in patients on dialysis. Calcium-based phosphate binders (eg, calcium carbonate, calcium acetate) frequently raise calcium levels, but sevelamer has a lesser effect on calcium and would not be adequate treatment for hypocalcemia.
Educational objective:
Postoperative hypoparathyroidism with resultant hypocalcemia is a common complication of thyroidectomy due to inadvertent injury or removal of the parathyroid glands. Postoperative supplementation with oral calcium and vitamin D can be used to treat and prevent postoperative hypocalcemia.